[FLINK-8639][State Backends]Fix always need to seek multiple times when
iterator RocksDBMapState
## What is the purpose of the change
This PR addressed issue
[FLINK-8639](https://issues.apache.org/jira/browse/FLINK-8639). Currently,
almost every time we want to iterator a RocksDBMapState we need to do seek at
least 2 times (Seek is a poor performance action for rocksdb cause it can't use
the bloomfilter). This is because `RocksDBMapIterator` use a `cacheEntries` to
cache the seek values every time and the `cacheEntries`'s init size is 1.
## Brief change log
- Change CACHE_SIZE_BASE from 1 to 32.
- Compare in reverse order in function underSameKey().
## Verifying this change
This change is already covered by existing tests.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (no)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/sihuazhou/flink improve_rocksdb_base_mapstate
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/5465.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #5465
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commit 753855ec2957492ba6c2eb272fdc5ffe7c769608
Author: summerleafs <summerleafs@...>
Date: 2018-02-12T14:28:04Z
1, Removed CACHE_SIZE_BASE, CACHE_SIZE_LIMIT.
2, Compare in reverse order in function underSameKey().
commit e33b807ba151265e0fd86d52701965dc5ffcb7be
Author: summerleafs <summerleafs@...>
Date: 2018-02-12T14:50:28Z
change CACHE_SIZE_BASE from 1 to 32.
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